#include <stdio.h>
#define SIZE 12
int main(){
	double finances[SIZE];
	double sum=0;
	for(int i=0;i<SIZE;i++)
	{
		scanf("%lf",&finances[i]);
		//printf("%lf\n",finances[i]);
		sum+=finances[i];
	}
	double result=sum/SIZE;
	printf("$%.2f\n",result);
	return 0;
}